Drying raw organic materials



1945' J. M. BAER 2,391,441

DRYING RAW ORGANIC MATERIALS Filed Npv. a. 1943 dIQ QOQOOOQQOOOO O09 60999 Patented Dec. 25, 1945 oFricE name RAW ORGANIC MATERIALS John M. Baer, Chicago, IlL, assignor to The Guardite Corporation, a corporation of Illlnois Application November 8, 1943, Serial No. 509,481

3 Claims. (CI. 34-45) This invention relates to a method of drying raw organic materials and primarily fruits, vegetables, and the like, containing a major proportion of water. l

The present invention relates to a method of drying predominantly watery products, while maintaining the product stable against reoxidation and uniform in its characteristics. Treatment according to this process in some instances has been found to leave a considerably higher vitamin content as,for example, vitamin C in potatoes than occurs with other methods.

In carrying out the process the product is cut into small pieces, preferably cubes about V; inch in cross-section or slices not more than inch thick. These are promptly subjected to a vacuum under which air is withdrawn therefrom.

They are then heated by means of steam coils or other source of heat while maintaining the.

source of radiant energy I! which may be maintalned above and below the product. In the drawing this is illustrated as steam coils, and a connection 13 to the boiler having return connection It are indicated. Additional energy may be supplied by superheated steam as indicated by the manifold l5 supplied with a number of vents It. A connection I! is also supplied leading to the vacuum pump. Appropriate means are provided for measuring the temperature in'the coils I! in the chamber l8 and so far as possible in the product. The thermocouple i9 is shown as indicating the temperature in the chamber, a thermocouple as indicating the temperature in the coils, and a thermocouple It as indicating the temperature in the product.

, It is to be understood that this illustration is diagrammatical only in order to illustrate the process described herein. Thus the food product may be supplied and removed continuously or in batches. The source may be steam or other radiant energy and may or may not be supplemented temperature of the product is relatively unimporploy higher pressures but in all cases it is preferred to maintain the pressure below 100mm. of mercury and preferably one not substantially above 60 mm. In such cases the temperature allowable may also be increased by adding to 100 F. the pressure in millimeters; that is, at 60 mm.

pressure the maximum temperature should be below 160 F. Similarly, .the diiierence between the temperature of the product and the temperature of the steam, which, at mm. should be from 30 to 45 F., may be correspondingly increased so that at 60 mm. it-is from 60 to 90 F.

The drying chamber may be. supplied with heat through steam coils arranged inside it or by radiant energy or by superheated steam.

vThe invention is illustrated diagrammatically in the drawing. The vegetable product it in the form of small slices or particles is placed upon a foraminous support II in close proximity, to a by superheated steam. The thermocouples will in general be supplied at various points throughout the system to obtain a composite temperature.

It has been found that it is dificult to measure accurately the temperature of the product itself undergoing treatment, and that a control based on measuring a predetermined temperature in the product is diflicult to apply. It has also been found relatively unimportant how hot the source of heat is, as for example the steam coils. A satisfactory control, however, may beestablished by correlating the temperature of the chamber itself to the pressure maintained therein. This may be accomplished either by comparison 01 the temperature of the chamber with the pressure, or by comparison of the temperature of the chamber with the roughly observed temperature of the product undergoing treatment.

' Appropriate readings may be taken by inserting thermocouples within the product which will give a reading satisfactory for the present purposes. The temperature of the atmosphere should be taken in such away as to shield the temperature recording means so far as possible from the eflects of the radiant heat.

For example, using a pressure of 20 to 25 mm.

of mercury, the temperature inside the chamber should rapidly be brought to a 'pealr below 150 F. and preferably below E, and should be maintained in this range throughout the drying 'operation even as the pressure is progressively product.

and preferably below 100 F. during the large bulk of the drying operation. During the latter stages, however, the product temperature may go above that or the chamber.

For example, using raw potatoes cutin /4 inch cubes, the cubed potatoes were placed ina vacuum chamber and subjected to an absolute pres sure of about 25mm. The chamber was heated by steam coils to which steam was supplied under an original pressure of 65 lbs. During the operation the pressure was gradually reduced, and

during the latter stages was cut of! entirely, the pipes themselves, however, having a residual heat content sufliclent to complete the drying. By the time that the chamber pressure had been re-- duced to 25 mm., the temperature of the chamher was 157 F. and the temperature of the prod uct was approximately 80 F. The chamber temperature, however, rapidly fell to less than 145 F. At the same time the pressure was slowly reduced and by the time it had fallen to 21 mm., the temperature of the product was about 100 F., and the chamber temperature about 132 F.

At this time the greater portion of the water had been removed and the resulting product was dry enough so that the vapor pressure of the water therein was markedly lower. The pressure in the chamber was then reduced progressively until it had fallen to 2.5 mm., during which time the temperature in the chamber likewise fell to around 126 F. On the other hand, the temperature of the product rose to' approximately 140 F. The original potatoes lost approximately 82% of their weight in the drying operation and the final material'was a white light-colored material which took up water readily upon immersion, was uniform in its characteristics, and did not discolor upon rewettingn The product had all of the culinary characteristics of raw potatoes and had a high vitamin C content.

Similar operations may be carried out on cabbage, carrots, onions, fruits and other predominantly aqueous vegetable materials.

. For example, carrots sliced to /8 inch in thickness were placed in a chamber and the pressure reduced to 23.5 mm., at which timev the chamber and vegetables at pressures of 5'7 mm.

The chamber temperature may be controlled by adjustment of the rate of evacuation, i. e., the pressure, andby the rate of supply of heat to the coils.

The atmosphere of steam referred to in the claims hereof may be produced by water evaporated from the product under treatment'or by supplying steam from an outside source.

Very effective results have been obtained upon potatoes, meat, vegetables and mixtures of meat This application is a, continuation-in-part of my co-pending application Serial No. 412,201,

temperature was 182 F. and the carrot temperature about 76 F. By the time that the carrot temperature had risen to 80 F.. the temperature of the chamberhad fallen to approximately 130 F. and the pressure to 20 mm. This ratio of temperature and pressure was maintained until the temperature 'of the carrots began to rise markedly, indicating substantial drying of the The pressure was then reduced progressively to as little as 1 mm., and the temperature of the chamber dropped to 116? F. In the meantime the temperature of the carrots rose'to about 140 F.

The' resulting product was dry, light, and re absorbed water readily. When rewetted it had the characteristics ofthe raw carrot.- Th product lost approximately 86% of its weight during the drying operation.

filed September 24, 1941.

The foregoing detailed description has been given for cleamesshof understanding only, and no unnecessary limitations should be understood therefrom.

What I claim as new, and desire to secure by Letters Patent, is:

1. In the drying of cellular organic products naturally containinga large percentage of moisture, the steps of subjecting the product in small particles in thin layers in an enclosed chamber forming a drying zone to a reduced pressure in an atmosphere of steam substantially free from air, supplying heat to the product'from a source of radiant energy in the chamber close to the product having a temperature within the drying zone markedly in excess of the temperature of saturated steam under the prevailing reduced pressure in the chamber, maintaining the product at a temperature of approximately to F. during the greater part of the drying operation, and maintaining the chamber temperature during the same time at 30 to 45 F. above the temperature of the product.

2. In the drying of cellular organic products naturally containing a large percentage of moisture, the steps of subjecting the product in small particles in thin layers in an enclosed chamber forming a drying zone to a. reduced pressure below 100 mm. of mercury in-an atmosphere of steam substantially free from air, supplying heat to the product from a source of radiant energy in the chamber close to the product having a temperature within the drying zone markedly in excess of the temperature of saturated steam under the prevailing reduced pressure in the chamber, maintaining the product at a temperature between approximately 100 F. and 00 F. plus the pressure in millimeters of mercury maintained on the product during the great- JOHN M. BAER. 

